In numerical control systems, an interactive-type automatic programming technique is widely used so that machining programs can be easily prepared in a short time. According to the interactive automatic programming procedure, the operator selects a menu screen displayed at a display device in accordance with a machining process, and then selects a menu item corresponding to a machining step, to thereby create a program. This procedure eliminates the need to use a complicated programming language such as an APT for preparing programs, thus permitting even an unskilled operator to create programs.
Machining programs thus created are stored in storage means such as a nonvolatile memory in the numerical control system. Accordingly, once a machining program is created, it can be fetched for use in another machining program. For example, if a hole-cutting program for cutting a hole according to a predetermined pattern is once created, it can be fetched and combined with another machining program to effect the same hole cutting. Thus, the collection of machining programs can be effectively used.
However, in cases where the number of created machining programs is large, each machining program must be selected and the contents thereof displayed, in order to examine whether the program contains a required machining step. Accordingly, finding a machining program containing a target machining step from among a large number of created machining programs is troublesome, requiring considerable labor and time.